The present invention relates generally to an intraluminal radiation system for the delivery of treatment elements by way of a catheter to a selected location within the intraluminal passageways of a patient. More particularly, the present invention relates to an improved transfer device for handling the treating elements and delivering them to the catheter and an improved catheter assembly.
Since the late 1970""s balloon angioplasty techniques have become widely used for opening blockages in coronary arteries. Briefly, the enlargement of the artery is achieved by advancing a balloon catheter into a narrowed portion of the artery and inflating the balloon to expand the diameter of the artery, thus opening the artery for greater blood flow. Atherectomy techniques, in which blockages are removed or reduced in size, have also been used to the same end.
While balloon angioplasty has proved an effective way of opening the coronary arteries, in a significant number of cases the arteries will narrow again at the location where the balloon was expanded, such narrowing being termed restenosis. Restenosis is believed to be caused by formation of scar tissue at the site of the angioplasty that results from the injury to the artery caused by the inflation of the balloon.
More recently, intraluminal radiation has been used after angioplasty or atherectomy to treat the affected area of the artery to inhibit cell proliferation and wound healing response and, consequently, help to prevent restenosis. Methods and apparatus for such intraluminal radiation treatment are disclosed in the co-pending application, serial No. 08/628,231, filed Apr. 4, 1996, which is incorporated herein by reference. This application generally discloses an apparatus comprising a catheter, which is inserted intraluminally into the patient and advanced to the site of the area to be treated, and a transfer device for facilitating either the hydraulic or pneumatic advancement and retrieval of individual radioactive treating elements or xe2x80x9cseedsxe2x80x9d along the catheter to and from the treatment site.
As with any device inserted into the vascular system, it must have sufficient integrity to insure that no pieces or elements are separated from or exit the device into the vascular system. This is particularly true for the treating elements which are moved to and from the distal end of the catheter. Additionally, because the device is intended to use radioactive treating elements, there is a heightened need for safety to prevent any unintended exposure of either the patient or the user to radioactivity.
Use of the apparatus described in the above-identified co-pending application has suggested several areas where the device could be improved to reduce the possibility of having treatment elements escape from the system, thus enhancing patient and user safety.
Consequently, it is the principal object of the present invention to provide a transfer device and catheter assembly that has additional safeguards to protect the patient and user.
More particularly, it is an object of the present invention to provide a transfer device/catheter assembly in which the catheter cannot be inadvertently detached from the transfer device unless all the treating elements reside within the transfer device. Similarly, it is an object of the present invention to provide a transfer device/catheter assembly in which none of the treating elements can exit the transfer device unless a catheter is connected thereto.
It is a further object to insure that the hydraulic or pneumatic pressures to which the transfer device/catheter assembly is subjected during the advancement and retrieval of the treating elements does not exceed a predetermined xe2x80x9csafexe2x80x9d pressure.
It is an additional object to provide a method and system for detecting the presence or absence of treating elements in the transfer device and for providing a visual indication of such presence or absence of treating elements.
These objects, and others that will become apparent upon reference to the following detailed description are accomplished in one aspect by an actuator assembly for the transfer device that includes a gate member that is moveable between a first position that prevents treating elements from entering the lumen of the catheter and a second position that permits treating elements to enter the lumen. The gate member is moveable into the second position only if the catheter is attached to the transfer device. The actuator assembly includes a switch member biased into a first position that prevents movement of the gate member into its second position unless the switch member is moved out of a first position that interferes with the movement of the gate member upon the catheter connector being received in the central opening of the transfer device. Additionally, a trigger member that is moveable into locking engagement with the connector when the connector is received in the central opening is disengageable by means of a separate release button.
In another aspect of the invention, a pressure indicator is provided that includes a transparent elongated cylinder viewable by the user of the transfer device and housing a piston which is slidingly received within the cylinder. The cylinder includes an inlet port through which pressurized fluid can enter, and the piston is biased so that the relative position of the piston and the cylinder provides a visual indication of the relative fluid pressure in the transfer device. The pressure indicator can include a portion having a inside diameter greater than that portion of the cylinder in which the piston is disposed and an outlet port in communication with the enlarged-diameter portion of the cylinder. Consequently, when the fluid pressure is sufficient to move the piston into the enlarged-diameter portion of the cylinder, fluid escapes passed the piston and exits the cylinder through the exit port. Alternatively, the pressure indicator can be connected and parallel fluid communication with a separate pressure relief valve of known construction.
In another aspect of the invention, the catheter includes a connector at its proximal end that is received in a central opening in the transfer device. The connector includes at least one detent for securing the connector in the central opening of the transfer device, the detent having to be manually actuable to release the catheter from the transfer device.
In a further aspect of the invention, a method is provided for determining whether the treating elements reside in the transfer device. The method includes encapsulating the treating elements in a material having a known wavelength/reflection ratios; shining to lights of different wavelengths into the area in the transfer device where the treating elements normally reside before and after being introduced into the catheter; measuring the reflectivety of the two lights as reflected off the area in the transfer device; determining the wavelength/reflection ratios of the reflected light; comparing the measured wavelength/reflection ratios with the known wavelength/reflection ratios; and indicating whether the measured ratios are substantially the same as the known ratios.
A system for accomplishing the method described above is another aspect of the invention and includes a power source; a first light source optically connected to the targeted location in the transfer device and that emits a light having a first wavelength; a second light source optically connected to the targeted location that emits light having a second wavelength; a photosensor optically connected to the targeted location that measures the light reflected off the targeted location and creating a signal corresponding thereto; a window detector for determining whether the signal created by photosensor is within a predetermined band corresponding to a signal which would be created by light of first and second wavelengths being reflected off the element; and an indicator light that is activated if the signal created by the photosensor is within the predetermined band.